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[ TPA2015D1 ] Efficiency Measurement

Kenichiro
Mastermind 9165 points
Other Parts Discussed in Thread: TPA2015D1

Hi,
My customer is having problem now on efficiency measurement on TPA2015D1EVM.
As long as they test this EVM, they can achieve around around 400mW Pout, but datasheet specify max output is around 2W.
Based on the guide line of audio performance measurement app. note, I'm still supporting customer.
http://www.ti.com/lit/an/sloa068/sloa068.pdf
Here is their conditions.
---
Load: 8ohm + 33uH
input: 1KHz single ended
VBAT: 3.6V
AGC: floating (no infection point)
GAIN: high (20dB)
---
So far I could not see any of suspicious on their evaluation set-up, except a resistor R4 is 0ohm.
(In the schematics of EVM, it's mentioned that R4 is 1kohm.)
Since customer use the function generator as input source with single end at JP IN jumper, they don's use RCA connector,
so left side of C1 is already short circuit to GND via JP SE jumper.
I still don't know why this happen, but do you think this is the reason why customer can't have enough output?
Sorry for less information, but it's appreciated if you give some comments on this matter.
Thanks,
Ken
tanaka-k@clv.macnica.co.jp
  • 0
    TI__Guru**** 189401 points

    Hi, Ken,

    The RCA input jack is a shorting type, so when nothing is plugged in, it will short out the inputs to the chip.

    You need to insert any RCA plug into the jack, and then feed the signal to JP IN, or alternately, get a BNC to RCA cable and use that to provide the input signal.

    -d2

  • 0 in reply to Don Dapkus
    Mastermind 9165 points

    Hi Don,

    Thank you for your reply!!

    I will try to use RCA jack and test again.

    Regards,

    Ken

    tanaka-k@clv.macnica.co.jp

  • 0 in reply to Kenichiro
    Mastermind 9165 points
    Hi Don,
    I tried to test TPA2015D1 EVM, but still bit confused whether this is valid or not.
    Can you help me to check whether my observation is correct?
     
    Signal Input Condition
    - Function Generator, single-ended
    - Signal goes to "JP IN" on EVM (with RCA cable which the other sde open)
    - 1KHz, 400mVpp setting
     
    TPA2015D1EVM Settings
    - GAIN: 20dB
    - AGC: disabled
    - VBAT: 3.6V, around 400mA
    - RL: 8ohm + 33uH
    - Low power filter mounted (1kohm + 4700pF, 33KHz fc)
     
    Observations
    - See attached waveforms.
    Ch1: Input signal (post input cap C1)
    Ch2: OUT- from "JP OUT"
    Ch3: OUT+ from "JP OUT"
    Math :OUT- - OUT+
     
     
    My questions are...
    Q: OUT- and OUT+ have almost same phase...why?
    (For efficiency measurement, is differential input signal necessary?)
     
    Q: Math shows almost square wave, even though input is sine wave...
     
     
    My customer's goal is ro measure the efficiency like fig. 5 in the datasheet.
    For efficiency measurement, if my set up is wrong, please let me know.
     
    Thanks,
    Ken
     
  • 0 in reply to Kenichiro
    Mastermind 9165 points
    Hi Don,
     
    Would you please check the discussion above?
     
    Thank you for your support in advance.
     
    Regards,
    Ken